Mitochondrial dysfunction and mtDNA polymorphisms have been associated with prostate cancer (PC) biology. We discovered a novel class of mitochondria-derived peptides (MDPs) that are transcribed from small open reading frames within the mtDNA. These include humanin, SHLP-2, and MOTS-c, which are circulating cytoprotective signaling peptides. Decreased MDP levels have been implicated in diseases of aging, and we recently found that Blacks have lower circulating levels of humanin and SHLP2 than Whites. We hypothesize that differences in MDP expression in minority men relative to Whites contribute to the elevated risk of PC. We seek to test the potential of plasma MDPs and their prostate expression levels as biomarkers for PC risk, both as pre-diagnostic biomarkers and as surrogate prognostic risk indicators in a group of men with and without PC including White, Latino, and Black men. We recently reported that in a small cohort of Black and White men undergoing prostate biopsy SHLP2 levels were significantly lower in men with PC vs. men without PC and that Black men had significantly lower levels than White men. A SHLP2 level >350 pg/ml had a negative predictive value of ?95% for a negative biopsy regardless of race and may be an excellent biomarker to avoid biopsy. A larger dataset is needed to validate our results, and this grant will dramatically expand this research question and look at additional ethnic groups and their subpopulations. Our first goal for this project includes the analysis of the association between serum SHLP2 levels and PC risk in ethnic minorities. We will leverage two ongoing sample collection efforts at UF and USC to analyze 700 serum samples from White, Latino, and Black men (Aim 1). SHLP2 levels will be compared between men with and without PC and stratified by race. Our second goal is to determine the association between additional plasma MDPs and PC risk among men of different ethnicities. We will measure plasma levels of humanin, MOTS-c, SHLP2, and SHLP6 and determine the association between these MDPs, race, and cancer status (Aim 2). Using whole transcriptome RNAseq analysis of RNA from micro-dissected FFPE from prostate tumor patients who are Black, White, and Latino we will compare the prostate mito-transcriptome for divergent expression of MDP transcripts and their relation to cancer severity and ethnic origin (Aim 3). Finally, we will examine the contribution of mitochondrial DNA copy number in the circulation and in benign and malignant prostate tissues, to PC risk and severity. Our study will be the first comprehensive study of racial differences in mtDNAcn, mitochondrial-derived peptide expression and levels, and their effect on PC. If successful, MDP levels may serve as diagnostic biomarkers of PC, particularly in minority men. The expected finding, that MDP levels are regulated by interventions that may modify cancer risk (such as diet and exercise, which raise MDP levels) could lead to a simple approach where at-risk men get their level measured and are counseled to make a lifestyle modification and never get the disease in the first place.